I have written numerous times about the arthritis problems in my thumbs. I suffer from osteoarthritis.This is the most common for of arthritis. Rheumatoid arthritis, however, is also a painful, if less common, affliction. Osteoarthritis (OA) is the most common type of arthritis. On the other hand, rheumatoid arthritis (RA) is recognized as the most crippling or disabling type of arthritis.

After studying immune cells taken from the joints of people with rheumatoid arthritis, scientists have found that once the disease sets in, some types of cell lose their sensitivity to vitamin D, according to Medical News Today.

The team — which comprised researchers from University College London and the University of Birmingham, both in the United Kingdom — reports the new findings in the Journal of Autoimmunity.

Rheumatoid arthritis is an autoimmune disease that arises because the immune system attacks healthy tissue — usually the joints — by mistake, leading to painful inflammation and swelling.

The disease often affects several joints at the same time, such as the knees, hands, and wrists. It inflames the lining of the joint and eventually damages the joint itself. This can lead to long-lasting pain, problems with balance, and deformity.

Estimates suggest that approximately 1 percent of the world’s population has rheumatoid arthritis, including around 1.3 million adults in the United States. It affects women more often than men, raising the question of whether hormonal factors may be involved. Study examined cells from inflamed joints

In their journal paper, the researchers explain that previous studies have revealed that vitamin D has “potent anti-inflammatory effects,” including the ability to suppress activity in some types of immune system T cell that are known to be active in rheumatoid arthritis.

However, those studies have only used immune cells isolated from blood, and so the impact of vitamin D on immune cells “at the site of active disease is unclear.”

A significant feature of the new study is that it is the first to use immune cells taken from both the blood and from the inflamed joints of people with rheumatoid arthritis.

“Unlike previous studies,” explains senior study author Karim Raza, a professor in the Institution of Inflammation and Ageing at the University of Birmingham, “we isolated different immune cell types from the actual site of disease to determine whether specific subsets of immune cells (specific T cell groups) have equal sensitivity to vitamin D.”

Immune cells lost sensitivity to vitamin D

For the investigation, the scientists used samples of synovial fluid taken from the joints of 15 people with rheumatoid arthritis aged between 40 and 85. Synovial fluid is a thick, sticky liquid that acts as a lubricant to reduce friction between bones that meet at joints.

They also examined blood samples taken from those with rheumatoid arthritis, and from individuals without rheumatoid arthritis — matched for the same age and gender — who had donated to a blood bank (the controls).

When they tested how immune cells in the different samples reacted to vitamin D, they found that some types of immune cell responded differently.

In particular, they found that some types of T cell taken from inflamed joints were less sensitive to the anti-inflammatory effects of vitamin D than those taken from the blood of the same people.